class Solution {
public:
    void dfs(vector<vector<char>>& grid, int i, int j)
    {
        int n = grid.size();
        int m = grid[0].size();
        grid[i][j] = '0';
        if (i - 1 >= 0 && grid[i - 1][j] == '1')
            dfs(grid, i - 1, j);
        if (i + 1 < n && grid[i + 1][j] == '1')
            dfs(grid, i + 1, j);
        if (j - 1 >= 0 && grid[i][j - 1] == '1')
            dfs(grid, i, j - 1);
        if (j + 1 < m && grid[i][j + 1] == '1')
            dfs(grid, i, j + 1);
    }
    int solve(vector<vector<char> >& grid)
    {
        int n = grid.size();
        if (n == 0)
            return 0;
        int m = grid[0].size();
        int count = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++)
            {
                if (grid[i][j] == '1')
                {
                    count++;
                    dfs(grid, i, j);
                }
            }
        }
        return count;
    }
};